py3-scapy is now scapy

OK bluhm sthen

Switch to scapy with python 3.

Remove echo headlines.

Do not create files as dependency of .BEGIN rule. Noticed by
deraadt@ with make obj in regress.

Rework when tests have to be skipped due to insufficient configuration
of the regress machine.

Simplify the detection for installed python and scapy. Refactor
these tests to make them similar. Use the setup and cleanup
variables.

Fix some comments and dependencies in this regress test.

Remove useless make depend targets.

This test cannot pass while pf on localhost filters packets statefully.
If the local pf is enabled, write a temporary stateless pass rule
into the regress anchor.

Print better error message if test fails.

Use netstat -n in target check-setup to avoid DNS timeout.
Requested by mpi@

Make the test faster. Move all the packet matching code into the
pcap filter. That means the first packet sniffed is the correct
one. In the success case, we can stop without waiting for a timeout

Make the test faster. Move all the packet matching code into the
pcap filter. That means the first packet sniffed is the correct
one. In the success case, we can stop without waiting for a timeout.
OK sashan@

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Add a test suite for pf state handling. It needs a remote machine
to exchange packets, the remote kernel is tested. For now it only
contains a challenge ack test written by sashan@.
OK sashan@